Are you saying that you have alot of banners on SoccerFriend.com? I count four (though it is late and my counting skills may not be so good...). I don't think that is excessive for the length of the page. You look at it this way: no matter where they are on the page, there is an advertisement there waiting for them to click.
remembers banners/advertising effects your existing traffic . if you donot have real contents or have excessive banners you may loose some visitors as peoples donot visit websites to buy products , they visit to get some useful information . So try to use less number of banner ads .. According to me there could not be any fixed number for it . it should depend on void spaces available on your website .
I don't think there's a fixed number for banners on a page. Make sure you don't place too many banners on a page which would make it spammy and unfriendly for a visitor.
It depends...if you can place in 10 without making the site look like crap and without compromising visitor experience and site quality...go for it I guess...but normally..it depends on what kinds of banners. I'd normally stick to 2...but that's just how I design my sites...a good designer can probably fit in lots more. (I guess 2 is a safe number for most)